Record whether a node is adopted and which modules were taken on it (hq ADR 0100)

internal/inventory/adoption.go

@@ -0,0 +1,149 @@
+package inventory
+
+import (
+	"context"
+	"errors"
+	"fmt"
+	"sort"
+)
+
+// A node is adopted or converged (novox/hq ADR 0100).
+//
+// Adopted: what is found on the machine is kept until its module is taken, and the firewall found
+// there stays in force. Converged: the machine is what the mesh declares, as every node was before
+// adoption existed. The controller is authoritative, and every declaration it sends says which.
+
+// ErrNotAdopted is taking a module on a node that is converged. On a converged node every assigned
+// module converges already; there is nothing to take.
+var ErrNotAdopted = errors.New("the node is converged, so every module on it is taken already")
+
+// ErrNotAssigned is taking a module that is not on the node. Taking is the cutover of a module
+// the node runs; one it does not run has nothing to cut over.
+var ErrNotAssigned = errors.New("that module is not assigned to the node")
+
+// SetAdopted makes a node adopted or converged. Becoming adopted stamps when; converging stamps
+// when too. Neither touches what was taken: what was taken stays taken when a node returns to
+// adopted, and converging takes the rest by its own act.
+func (i *Inventory) SetAdopted(ctx context.Context, name string, adopted bool) error {
+	node, err := i.NodeByName(ctx, name)
+	if err != nil {
+		return err
+	}
+	if node.Adopted == adopted {
+		return nil
+	}
+	if adopted {
+		_, err = i.store.Pool().Exec(ctx,
+			`update node set adopted = true, adopted_since = now() where id = $1`, node.ID)
+		return err
+	}
+	_, err = i.store.Pool().Exec(ctx,
+		`update node set adopted = false, adopted_since = null, converged_at = now() where id = $1`,
+		node.ID)
+	return err
+}
+
+// Take records that a module has been taken on an adopted node: its cutover. From then on the
+// module's resources converge on that node like any other, replacing what was found.
+//
+// Refused on a converged node and for a module not assigned there. Taking again is not an error;
+// the first time it was taken is kept.
+func (i *Inventory) Take(ctx context.Context, nodeName, module string) error {
+	node, err := i.NodeByName(ctx, nodeName)
+	if err != nil {
+		return err
+	}
+	if !node.Adopted {
+		return fmt.Errorf("%w: %s", ErrNotAdopted, nodeName)
+	}
+	return i.take(ctx, node, module)
+}
+
+// take is Take without the adopted check, for converging, which takes every assigned module in
+// the same act that makes the node converged.
+func (i *Inventory) take(ctx context.Context, node Node, module string) error {
+	var assigned bool
+	if err := i.store.Pool().QueryRow(ctx,
+		`select exists (select 1 from assignment where node = $1 and module = $2)`,
+		node.ID, module).Scan(&assigned); err != nil {
+		return err
+	}
+	if !assigned {
+		return fmt.Errorf("%w: %s is not on %s; assign it first", ErrNotAssigned, module, node.Name)
+	}
+	_, err := i.store.Pool().Exec(ctx,
+		`insert into taken (node, module) values ($1, $2) on conflict do nothing`, node.ID, module)
+	return err
+}
+
+// Converge makes an adopted node converged in one act: every module assigned there is taken, and
+// the node is recorded converged. Returned is what this act took, in name order.
+func (i *Inventory) Converge(ctx context.Context, nodeName string) ([]string, error) {
+	node, err := i.NodeByName(ctx, nodeName)
+	if err != nil {
+		return nil, err
+	}
+	if !node.Adopted {
+		return nil, fmt.Errorf("%s is converged already", nodeName)
+	}
+	tx, err := i.store.Pool().Begin(ctx)
+	if err != nil {
+		return nil, err
+	}
+	defer func() { _ = tx.Rollback(context.WithoutCancel(ctx)) }()
+	rows, err := tx.Query(ctx,
+		`insert into taken (node, module)
+		 select node, module from assignment where node = $1
+		 on conflict do nothing
+		 returning module`, node.ID)
+	if err != nil {
+		return nil, err
+	}
+	var took []string
+	for rows.Next() {
+		var m string
+		if err := rows.Scan(&m); err != nil {
+			rows.Close()
+			return nil, err
+		}
+		took = append(took, m)
+	}
+	rows.Close()
+	if err := rows.Err(); err != nil {
+		return nil, err
+	}
+	if _, err := tx.Exec(ctx,
+		`update node set adopted = false, adopted_since = null, converged_at = now() where id = $1`,
+		node.ID); err != nil {
+		return nil, err
+	}
+	if err := tx.Commit(ctx); err != nil {
+		return nil, err
+	}
+	sort.Strings(took)
+	return took, nil
+}
+
+// Taken is every module taken on a node, in name order — including one no longer assigned there:
+// unassigning does not un-take.
+func (i *Inventory) Taken(ctx context.Context, nodeName string) ([]string, error) {
+	node, err := i.NodeByName(ctx, nodeName)
+	if err != nil {
+		return nil, err
+	}
+	rows, err := i.store.Pool().Query(ctx,
+		`select module from taken where node = $1 order by module`, node.ID)
+	if err != nil {
+		return nil, err
+	}
+	defer rows.Close()
+	var out []string
+	for rows.Next() {
+		var m string
+		if err := rows.Scan(&m); err != nil {
+			return nil, err
+		}
+		out = append(out, m)
+	}
+	return out, rows.Err()
+}